COLOR TRANSFORMATION METHOD AND CORRESPONDING COLOR DISPLAY METHOD
A color transformation method includes following steps. First, a color signal is received. Then, a saturation calculation step is performed to generate a saturation value of the color signal, and a hue-angle-weighting calculation step is performed to generate a first hue-angle weighting of the color signal corresponding to a first LUT and a second hue-angle weighting of the color signal corresponding to a second LUT. Next, a color calculation step is performed to transform the color signal into a first color output signal according to the saturation value and the first hue-angle weighting and to transform the color signal to a second color output signal according to the saturation value and the second hue-angle weighting.
1. Field of the Invention
The present invention relates to a color transformation method and a corresponding color display method, and more particularly, to a color transformation method and a corresponding color display method used by a display device with two backlights so as to raise a color gamut.
2. Description of the Prior Art
Traditional displays mix three primary colors of red, green and blue in a single pixel to display a required color, and a required image can be displayed by combining a plurality of pixels displaying different colors. Because the displayed color in the pixel is mixed by the three primary colors which are predetermined by the display, the displayed color is limited to a color gamut which is composed of the three primary colors, so that the display can not display a correct color of an image.
The prior art methods for raising the color gamut can be divided into two kinds, which respectively are a color mixing method in space and a color sequential method. The methods of the prior art mainly use increasing the number of the mixed color to achieve mixing multiple primary colors, so that the color gamut can be raised. Please refer to
In addition, a color sequential method utilizes a color transformation matrix to transform three inputted primary-color signals from gray-level signals into XYZ color-space signals. Then, a multiple primary-color algorithm is performed to transform the XYZ color-space signals into four primary-color signals C1, C2, C3 and C4. Finally, the primary-color signals C1, C2 are projected by a first projecting device, and the primary-color signals C3, C4 are projected by a second projecting device, so that the primary-color signals C1, C2, C3 and C4 can be mixed to raise the displayed color gamut.
However, according to the above-mentioned description, the color mixing method in space of the prior art is required to increase color filters with different colors in each pixel, so that extra processes should be performed to manufacture the increased color filters with different colors. The manufacture cost is therefore increased. Furthermore, the color sequential method of the prior art is required to use the color transformation matrix to transform three primary-color signals from the gray-level signals into the XYZ color-space signals, so that a plurality of multipliers and adders should be required. For this reason, the complexity of circuit devices and the number of devices are increased, and manufacturing the circuit devices is not easy. Therefore, to raise the color gamut and to simplify the circuit devices and the complexity of manufacturing process is an objective that industry aims to achieve.
SUMMARY OF THE INVENTIONIt is therefore a primary objective to provide a color transformation method and a corresponding color display method to raise color gamut.
According to a preferred embodiment, a color transformation method is disclosed. First, a color signal is received. Then, a saturation calculation step is performed to generate a saturation value of the color signal through a saturation operator, and a hue-angle-weighting calculation step is performed to generate a first hue-angle weighting of the color signal corresponding to a first look-up table (LUT) and a second hue-angle weighting of the color signal corresponding to a second LUT. Next, a color calculation step is performed to transform the color signal into a first color output signal according to the saturation value and the first hue-angle weighting, and to transform the color signal to a second color output signal according to the saturation value and the second hue-angle weighting through a color operator.
According to a preferred embodiment, a color display method is disclosed. First, the color signal is transformed into the first color output signal and the second color output signal by an operator according to the color transformation method of the present invention. Next, the first color output signal and the second color output signal is outputted to a display device in sequence, wherein the display device comprises a first backlight and a second backlight. Then, the first color output signal is displayed, and the first backlight is simultaneously turned on. Finally, the second color output signal is displayed, and the second backlight is simultaneously turned on.
As the above-mentioned description, the color transformation method of the present invention calculates the saturation value and two hue-angle weightings of the color signal, and then, performs the color calculation step corresponding to two backlights so as to generate two different color output signals. Furthermore, in cooperation with sequentially turning on the backlights, more colorful images can be displayed, and the color gamut can be raised.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Please refer to
Step S100: input a color signal 112 to an operator 104 by the image input unit 102;
Step S200: transform the color signal 112 into a first color output signal 114 and a second output signal 116 by the operator 104 according to a color transformation method;
Step S300: output the first color output signal 114 and the second color output signal 116 to the display device 106 in sequence;
Step S400: input the first color output signal 114 to a pixel unit so as to display the first color output signal 114, and turn on the first backlight simultaneously; and
Step S500: input the second color output signal 116 to the same pixel unit so as to display the second color output signal 116, and simultaneously turn off the first backlight 108 and turn on the second backlight 110.
In addition, please refer to
Please refer to
In order to cooperate with the step of sequentially turning on the first backlight 108 and the second backlight 110 so as to display the color in the hybrid color gamut, the color transformation method of the present invention will be detailed in the following description. Please refer to
Step S220: receive a color signal 112;
Step S230: perform a saturation calculation step to generate a saturation value of the color signal through a saturation operator, and perform a hue-angle-weighting calculation step to generate a first hue-angle weighting of the color signal corresponding to a first look-up table (LUT) and a second hue-angle weighting of the color signal corresponding to a second LUT; and
Step S240: perform a color calculation step to transform the color signal to a first color output signal according to the saturation value and the first hue-angle weighting and to transform the color signal to a second color output signal according to the saturation value and the second hue-angle weighting through a color operator.
In step S220, the received color signal 112 of this embodiment includes a first primary color gray value 146, a second primary color gray value 148 and a third primary color gray value 150. In this embodiment, the first primary color gray value 146, the second primary color gray value 148 and the third primary color gray value 150 are respectively a red gray value 146, a green gray value 148 and a blue gray value 150, but are not limited to these. The colors of the first primary color gray value 146, the second primary color gray value 148 and the third primary color gray value 150 also can be other colors. For example, the colors of the first primary color gray value, the second primary color gray value and the third primary color gray value are respectively yellow, magenta and cyan.
In step S230, the saturation calculation step is performed according to a saturation calculation formula w=1-min/max, and the saturation value of the color signal 112 is generated by the saturation operator 140, wherein w is the saturation value; min is a minimum among the red gray value 146, the green gray value 148 and the blue gray value 150; and max is a maximum among the red gray value 146, the green gray value 148 and the blue gray value 150. For example, a combination of the inputted red gray value 146, the inputted green gray value 148 and the inputted gray value 150 are respectively (255, 0, 0). The maximum is the red gray value 146, and is 255. The minimum is the green gray value 148 or the blue gray value 150, and is 0. Therefore, the saturation value w can be calculated to be 1.In another example, a combination of the inputted red gray value 146, the inputted green gray value 148 and the inputted gray value 150 are respectively (255, 253, 200). The maximum is the red gray value 146, and is 255. The minimum is the blue gray value 150, and is 200. Therefore, the saturation value w can be calculated to be 0.2157. The saturation calculation formula of the present invention is not limited to the above-mentioned formula, and can be adjusted according to the real requirements.
In addition, please refer to
Step S232: perform a hue-angle calculation step to calculate a hue angle composed of the first primary color gray value 146, the second primary color gray value 148 and the third primary color gray value 150 through a hue-angle operator 142; and
Step S234: perform a look up step to look up a first hue-angle weighting corresponding to the hue angle from the first LUT and to look up the second hue-angle weighting corresponding to the hue angle from the second LUT.
Please refer to
As shown by the hue angle H (×64) in
Furthermore, in step S234, the first LUT and the second LUT are calculated according to the first color gamut of the first backlight and the second color gamut of the second backlight. Please refer to
Please refer to
As the above-mentioned description, this embodiment calculates the saturation value and two hue-angle weightings of the color signal, and transforms the color signal into two color output signals corresponding to two backlights, so that the color gamut of the displayed color can be raised in cooperation with turning on the backlights in sequence so as to display more plentiful colors. As compared with the prior art that transforms the gray-level signal into XYZ color-space signal, the present invention can have an effect of mixing multiple primary colors only by the saturation operator, the hue-angle operator and color operator in cooperation with two backlights, and avoid consuming extra operators due to extra matrix operation. Furthermore, the present invention only requires disposing three color filters in one pixel, so that the increased complexity of circuit devices and extra costs of manufacturing extra color filters can be avoided. It should be noted that the present invention is not limited to only using two backlights, and is not limited to only calculating two color output signals. The present invention also can use a plurality of backlights in cooperation with calculating a plurality of color output signals to provide a more colorful image.
In addition, the color transformation method of the present invention is not limited to the above-mentioned embodiment, and also can include a gamma correction step, a de-gamma correction step or a color space transforming step. Please refer to
Step S220: receive a color signal 112;
Step S230: perform a saturation calculation step to generate a saturation value of the color signal 112 through a saturation operator 142, and perform a hue-angle-weighting calculation step to generate a first hue-angle weighting of the color signal 112 corresponding to a first LUT and a second hue-angle weighting of the color signal 112 corresponding to a second LUT;
Step S250: perform a gamma correction step to transform a gray value of the color signal 112 into a luminance value by the gamma voltage transformation device 202;
Step S260: perform a color-space transformation step to transform the color signal 112 into a first color-space signal 208 by a first color space operator 206 and to transform the color signal 112 into a second color-space signal 212 through a second color space operator 210;
Step S240: perform a color calculation step to transform the first color-space signal 208 into a first color output signal 114 according to the saturation value and the first hue-angle weighting and to transform the second color-space signal 212 into a second color output signal 116 according to the saturation value and the second hue-angle weighting by the color operator 144; and
Step S270: perform a de-gamma correction step to transform luminance values of the first color output signal 114 and the second color output signal 116 into gray values.
In step S250, the gamma correction step is used to avoid unfitting feeling of the human eyes for the motion image due to the obvious difference between the color displayed after calculating the color signals and the color of the image sensed by the human eyes. For this reason, the first primary color gray value, the second primary color gray value and the third primary color gray value of the inputted color signal 112 are respectively transformed into the first primary color luminance value, the second primary color luminance value and the third primary color luminance value so as to have more correct hybrid color and contribute to perform the color calculation in the following step. Furthermore, in step S260, this embodiment uses the first backlight and the second backlight to design a first color transformation matrix M1 and a second color transformation matrix M2. In the color-space transformation step, the first color space operator 206 can multiply the first primary color luminance value, the second primary color luminance value and the third primary color luminance by the first color transformation matrix M1 to generate a first color space luminance value, a second color space luminance value and a third color space luminance value, which constitute a first color-space signal 208, and the second color space operator 210 can multiply the first primary color luminance value, the second primary color luminance value and the third primary color luminance by the second color transformation matrix M2 to generate a fourth color space luminance value, a fifth color space luminance value and a sixth color space luminance value, which constitute a second color-space signal 212. Therefore, the first primary color luminance value, the second primary color luminance value and the third primary color luminance value can be transformed into the color space of the first backlight and the color space of the second backlight so as to avoid the color deviation while displaying the first color output signal 114 and the second color output signal 116 in the following step. In this embodiment, M1 can be
The present invention is not limited to this, and can be adjusted or designed according to the required first color gamut and the required second color gamut. Next, as compared with the first embodiment, step S240 of this embodiment uses the first color space luminance value, the second color space luminance value and the third color space luminance value to calculate the first color calculation formula RGB1=RGB−w×k1×RGB, and uses the fourth color space luminance value, the fifth color space luminance value and the sixth color space luminance value to calculate the second color operating formula RGB2=RGB−w×k2×RGB so as to have the first color output signal 114 and the second color output signal 116 represented by the luminance values. Finally, in step S270, the de-gamma correction step transforms the luminance values of the first color output signal 114 and the second color output signal 116 that is transformed by the gamma correction step before into the gray values so as to help the display device to display.
In summary, the color transformation method of the present invention calculates the saturation value and two hue-angle weightings of the color signal, and then, performs the color calculation step corresponding to two backlights so as to generate two different color output signals. Furthermore, in cooperation with sequentially turning on the backlights, more colorful images can be displayed, and the color gamut can be raised.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.
Claims
1. A color transformation method, comprising:
- receiving a color signal;
- performing a saturation calculation step to generate a saturation value of the color signal through a saturation operator, and performing a hue-angle-weighting calculation step to generate a first hue-angle weighting of the color signal corresponding to a first look-up table (LUT) and a second hue-angle weighting of the color signal corresponding to a second LUT; and
- performing a color calculation step to transform the color signal into a first color output signal according to the saturation value and the first hue-angle weighting, and to transform the color signal to a second color output signal according to the saturation value and the second hue-angle weighting by a color operator.
2. The color transformation method of claim 1, wherein the color signal comprises a first primary color gray value, a second primary color gray value and a third primary color gray value.
3. The color transformation method of claim 2, wherein the saturation calculation step is performed according to a saturation calculation formula w=1-min/max, wherein w is the saturation value, min is a minimum of the first primary color gray value, the second primary color gray value and the third primary color gray value, and max is a maximum of the first primary color gray value, the second primary color gray value and the third primary color gray value.
4. The color transformation method of claim 2, wherein the hue-angle-weighting calculation step comprises:
- performing a hue-angle calculation step to calculate a hue angle composed of the first primary color gray value, the second primary color gray value and the third primary color gray value through a hue-angle operator; and
- performing a look up step to look up the first hue-angle weighting corresponding to the hue angle from the first LUT and to look up the second hue-angle weighting corresponding to the hue angle from the second LUT.
5. The color transformation method of claim 4, wherein the hue-angle calculation step comprises:
- judging a magnitude relation between the first primary color gray value, the second primary color gray value and the third primary color gray value so as to have a maximum, a medium and a minimum; and
- calculating the hue angle according to a hue-angle calculation formula H=θ+60×((the medium−the minimum)/(the maximum−the minimum)), wherein H is the hue angle; when the maximum is a red gray value, the medium is a green gray value, and the maximum is larger than the medium, θ is zero degree; when the maximum is the green gray value, and the medium is the red gray value, θ is 60 degrees; when the maximum is the green gray value, the medium is a blue gray value, and the maximum is larger than the medium, θ is 120 degrees; when the maximum is the blue gray value, and the medium is the green gray value, θ is 180 degrees;
- when the maximum is the blue gray value, and the medium is the red gray value, θ is 240 degrees; and when the maximum is the red gray value, the medium is blue gray value, and the maximum is larger or equal to the medium, θ is 300 degrees.
6. The color transformation method of claim 4, wherein the first LUT and the second LUT are derived from calculating a first color gamut of a first backlight and a second gamut of a second backlight.
7. The color transformation method of claim 4, wherein the first backlight is composed of a plurality of first light-emitting units with the first color gamut, and the second backlight is composed of a plurality of second light-emitting units with the second color gamut.
8. The color transformation method of claim 7, wherein the first light-emitting units and the second light-emitting units located in a same row are arranged alternately, and the first light-emitting units and the second light-emitting units located in a same column are arranged alternately.
9. The color transformation method of claim 7, wherein each first light-emitting unit comprises a first color LED, a second color LED and a third color LED, and each second light-emitting unit comprises a fourth color LED, a fifth color LED and a sixth color LED.
10. The color transformation method of claim 1, wherein the color calculation step is performed according to a first color calculation formula RGB1=RGB−w×k1×RGB and a second color calculation formula RGB2=RGB−w×k2×RGB, wherein RGB1 is the first color output signal, RGB2 is the second color output signal, RGB is the color signal, w is the saturation value, k1 is the first hue-angle weighting, and k2 is the second hue-angle weighting.
11. The color transformation method of claim 1, further comprising performing a color-space transformation step after the step of receiving the color signal to transform the color signal into a first color-space signal through a first color-space operator and to transform the color signal into a second color-space signal through a second color-space operator.
12. The color transformation method of claim 1, further comprising performing a gamma correction step between the step of receiving the color signal and the step of performing the color calculation step to transform a gray value into a luminance value of the color signal, and performing a de-gamma correction step after the step of performing the color calculation step to transform luminance values of the first color output signal and the second color output signal into gray values.
13. A color display method, comprising:
- transforming the color signal into the first color output signal and the second color output signal by an operator according to the color transformation method of claim 1;
- outputting the first color output signal and the second color output signal to a display device in sequence, wherein the display device comprises a first backlight and a second backlight;
- displaying the first color output signal, and simultaneously turning on the first backlight; and
- displaying the second color output signal, and simultaneously turning on the second backlight.
Type: Application
Filed: Aug 5, 2009
Publication Date: Nov 18, 2010
Patent Grant number: 8384731
Inventors: Pei-Lin Hsieh (Taipei County), Yu-Ju Lee (Taoyuan County), Hsiang-Tan Lin (Keelung City)
Application Number: 12/535,700
International Classification: G09G 5/02 (20060101);